Shearing unit

ABSTRACT

A shearing unit for sheep and removing wool from a pelt by an endless or rotary cutter having a serrated cutting edge to operate at high speed. The endless belt cutting blade (1) is supported by a frame (3) with a comb (4) to maintain distance between the cutting blade (1) and the skin (5).

This invention relates to an improved shearing unit, and moreparticularly to a shearing unit which includes an improved cutter forshearing the wool off a sheep.

BACKGROUND OF THE INVENTION

Conventionally shearing is carried out manually by using a hand piecewhich includes a cutter having cutting teeth moving over a stationarycomb, the teeth oscillating or reciprocating back and forth over theteeth of the comb.

Work has been carried out for the mechanised shearing of sheep, theseeither being fully or partially mechanised but as far as is known, theseall include a shearing mechanism or head which includes a similar formof reciprocating cutter.

The inherent disadvantages of these known cutters are well known, suchas the mechanism required to convert the rotary motion into thereciprocating, motion, noise, and the need to frequently sharpen boththe cutter and the comb.

Also due to the form of cutter and comb a considerable force is requiredin order for the fingers of the comb to penetrate the wool so that thecutter itself can cut the wool by acting with a scissor type actionbetween the edges of the cutter blade and the fingers of the comb.

Attempts have been made to develop a non-reciprocating cutter byutilizing a sharpened blade which continuously moves in one directionand which may not need to co-operate with a stationary comb. Howeverthese have not been entirely successful due apparently to the fact thatthe sharpened and honed edge quickly becomes dulled and blunt, and alsothat if any rate of movement of the cutter through the wool isattempted, then the wool is not cut but is laid down beneath the cutter.

In U.S. Pat. No. 3,535,744 there is disclosed an apparatus and methodfor severing fleece from a sheep pelt, and which uses an endless beltknife in order to sever the fleece from the pelt. This endless beltknife is honed to a sharp edge, and the knife belt is continuouslysharpened by grinding wheels rotated on a lower run of the knife belt,this knife belt being sharpened both sides by the pair of grindingwheels.

It is an object of this invention to provide a continuous oruni-directional cutter suitable for the shearing and cutting of wool andwhich cutter does not have to be continuously sharpened.

BRIEF STATEMENT OF THE INVENTION

Thus there is provided according to this invention a shearing unithaving a cutting head, the cutting head having a cutting bladecontinuously moving in one direction, the edge of the blade having aserrated or serrulate edge whereby these serrations grip and cut thefibres of the wool.

The cutting blade can either be a hand piece having a disc to rotate ata high speed or an endless belt form of blade with the cutting surfaceor edge of the disc or belt being provided with the finely serrated orserrulate edge to mechanically shear a sheep on a shearing cradle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an endless belt blade shearing the fleece from the body ofa sheep,

FIG. 2 shows the edge of a razor blade magnified ten times,

FIG. 3 shows a blade which is produced by a grinding stone having arating of 46 grit,

FIG. 4 shows a photograph of a blade produced with a stone 35 grit,

FIG. 5 shows a blade ground with a 60 grit stone and,

FIG. 6 shows a rotary form of cutter

A DESCRIPTION OF THE PREFERRED EMBODIMENT

The wool industry throughout the world has been seeking alternativemethods of severing wool fibres and to date it has been felt fromexperience that the use of a band cutter or rotary cutter was a conceptwhich was not technically feasible as a severance method.

A smooth cutting edge, such as a knife or razor edge depends for itscutting effect on the pressure that can be applied between the fibre andthe cutting blade. This pressure or force can be increased by theintroduction of friction from longitudinal movement of the blade.However with a smooth edge these forces are limited depending on theresistance of the fibres to the pressure applied and this decreased awayfrom the root of the fibre because of the cantilever effect.

In shaving the blade edge is applied as close as possible to the root ofthe fibre so that the forces necessary to sever the fibres can beapplied.

However it is not practical to shave sheep. A minimum length of residualfibre is required for protection against the elements. The cantilevereffect introduced reduces the effective pressure that can be applied tothe cutting edge making it practically ineffective.

The introduction of the sharp but serrated edge introduces an entirelynew principle. Only pressure sufficient to engage or enter the fibresinto the serrations is required. Having entered the serrations they arethen subjected to the chopping or cutting impact applied by theserrations of the fast moving blade and the severance of the fibres isnow mostly effected in the direction of the movement of the blade. Thecontact is no longer a gentle pressure but rather the impact of achopping effect by the serrated edges on the fibres themselves.

While any developmental work up to date has apparently been influencedby the traditional method of shearing based on conventional hand shearblades or reciprocating blades each of which relay on a scissor action,the attempts which have been made to adapt a smooth honed cutting edgeto a free cutting method results in the fibre laying down in front ofthe blade when an acceptable rate of cutting is attempted. A honed bladerelies on the sharpness of the edge to sever the fibre when drawn acrossthe fibres.

Thus the work by the inventor has established a new and efficient methodof severance, in that a sharp and rough or serrated edge moving at asufficiently high speed cutting close to the root of the fibre willsever the fibres with no observable displacement. This cutting edge iscreated by using a relatively rough grinding stone to produce sharpserrations that engage the fibres which are then subject to the impactof the speed of the moving blade.

In effect the cutting action is in the direction of the movement of theblade along its length rather than perpendicular to it. Within practicallimits the cutting efficiency of the blade is related to its speed ofmovement.

In moving the blade into the fleece to engage the fibres some pressuremust be applied which must result in some laying over of the fibres. Theamount of pressure that must be applied is dependent on maintaining theefficiency of the cutting edge and the rate of cutting. The resultingangle of laying over is then a function of where this pressure isapplied, it will be less when cutting close to the skin and greater whencutting at a distance therefrom.

FIG. 1 shows one example of a shearing unit which can be utilised toshear a major portion of the fleece a sheep. The Fig. shows one form ofshearing unit in which the cutting element is an endless blade 1 guidedin a guide track 2 mounted on a support frame 3.

The guide track is also provided with a short comb 4 which protrudeswith its fingers only slightly ahead of the cutting blade. The mainpurpose of the comb is to create a distance between the cutting bladeand the skin of the sheep 5 to leave the required length of wool on thebody of the sheep.

The shearing unit is also provided with a pair of driven rollers 6 and 7which assist in moving the sheep around and rotating the sheep, androller 7 could be driven at a slightly higher speed than roller 6 sothat the skin of the sheep is maintained in a taut condition.

There is a space provided in the guide track immediately behind thecutting edge this space 8 being provided to prevent the fibres beingdrawn between the teeth of the comb and the cutting blade.

The blade is inclined to the normal to the body of the sheep, and asshown this could be in the vicinity of 15 degrees.

The form of shearing cradle as shown in my earlier Australian PatentApplication No. 53982/79 can have incorporated therein the cutting bladeof the present invention, with the sheep restrained by means as shown inmy Australian Pat. No. 501826. Hence it is merely necessary for theshearer to clamp the sheep in position, and skirt the fleece by shearingthe legs, belly and head. The shearer then opens the fleece by ashearing cut to present a face of the wool along the side of the sheepup to the shoulder. This opening cut is then presented to the knife andby turning and rolling the sheep, the fleece is shorn from the sheep.Hence up to 80% of the sheep is shorn mechanically.

As shown in FIG. 2 there is illustrated the edge of a typical razorblade which is honed to a sharp edge this photograph being taken at amagnification 10 times.

FIG. 3 shows a cutting blade which has been provided with an edge causedby a grinding stone having a grit of 46. For comparisons FIG. 4 shows anedge produced by a 35 grit stone while FIG. 5 shows an edge produced bya 60 grit stone.

It will be seen that these produce an edge having a roughened andserrated edge these serrations being such that the roughness can bereadily felt by drawing a finger nail over the edge of the cuttingblade.

For convenience the roughness of the blade can best be defined as thatproduced by the range of grits, and it has been found that the desiredserrations can be provided by grits having the range of 30 to 120 grit.

Where reference is made to "grit" this is the standard approved by theAbrasive Grain Association and Grinding Wheel Manufacturers Association.

As shown in FIG. 1 the angle of the blade to the normal of the cuttingsurface is effected by various factors. This includes the requiredclearance behind the cutting edge for the free passage of the residualfibres, and to compensate for the angle of laying over of the fibres inorder to maintain a satisfactory angle of presentation of the cuttingedge to the fibres.

In order to meet the above requirements it is necessary to vary thisangle for different operational conditions, whether the wool is of afine wool or a coarser wool.

The speed of the blade effects the rate at which the fibres aresatisfactorily severed. That is the rate of feed of the fibres to theblade can be increased with increased blade speed but it is to be notedthat there is obviously an operating practical limit.

The effect of these relative speeds can be observed by studying thelength of the residual fibre. The length of the residual fibre increasedwith increased feed of fibres that is an increase laying over of thefibres in front of the blade.

However by increasing the speed of the blade this increases the impacteffect of the serrations on contact with the fibres. It has been foundthat at speeds of the order of 1,500 meters per minute the efficiency ofthe cutting operation is greatly improved over speeds of 1,000 metersper minute and it is felt that an operational limit of about 3,000meters per minute would be achieved.

It is necessary to maintain an efficient cutting edge on the blade andthis will depend on various factors, (1) the gauge or thickness of thefibres (2) the density of the fibres and (3) foreign material (sand etc.present in the fleece).

Under a given set of conditions of operation the efficiency of thecutting edge can be observed by comparing the length of the residualfibres that exist for a known speed of blade, height of cut and angle ofpresentation. The remaining variable factor is the sharpness of theserrations, as these wear or become dulled the residual fibres willincrease in length.

However it is possible to treat the edge of the blade with a selectedstone during the process of removal to maintain its cutting efficiency.

The serrations are produced by the grits moving across the cutting edge.The speed of the blade and the peripheral speed of the stone affect theangle of presentation of the stone to the blade to produce the desiredangle of serrations to engage the fibres.

Grinding stones may vary in hardness and grit size and the cuttingeffect can vary with variations in each. The cutting effect to producethe serrations required also varies with the hardness of the blade used.For a given set of circumstances a stone of a particular grit size andhardness or softness is selected to produce the desired optimumroughness of the serration.

It will be seen that with the present invention there is provided acutting unit which will effectively cut and shear the wool from a sheepwith the cutting unit having a continuous direction of movement whetherthis be a rotary unit as illustrated in FIG. 6 or an endless blade typeshown in FIG. 1 the type in FIG. 6 being useful as a hand piece in whichthe forward force to present the cutter blade to the wool is reduced dueto the fact that there are no teeth or comb-like fingers to be pushedthrough the wool before the cutter blade acts on the wool to sever thewool, the small comblike fingers do not present an appreciable force tothe forward movement.

I claim:
 1. A shearing unit for shearing wool from a pelt or skin of asheep, said unit comprising a head having an endless cutting blade,means to drive said endless cutting blade, and a comb to space saidblade from the pelt or skin, characterised in that said comb essentiallyprovides no support or restraint on the fibres of the wool and saidendless cutting blade is provided with a serrated cutting edge, theserrations being of a size corresponding to that produced by a grindingstone selected within the range of 30 to 120 grit, whereby at highcutting speeds said serrated edge cuts the wool by the serrationsimpacting on the unsupported and unrestrained fibres of the wool.
 2. Ashearing unit as defined in claim 1 characterised in that the serrationscorrespond to a size produced by a 60 grit stone.
 3. A shearing unit asdefined in claim 1 characterised in that the endless cutting bladeoperates at a linear speed of 500 to 3,000 meters per minute.
 4. Ashearing unit as defined in claim 1 characterised in that the endlesscutting blade operates at a linear speed of 1,500 meters per minute. 5.A shearing unit as defined in claim 1 characterised in that said cuttingblade is a rotary cutter.
 6. A shearing unit as defined in claim 1characterised in that said cutting blade is an endless belt cutter.
 7. Ashearing unit as defined in claim 1 characterised by a space behind saidcutting blade to prevent fibres being drawn along the blade.